Overexpression of transcription factors Mafa and Pdx1 induces in-vivo transdifferentiation of pancreatic α cells to β-like insulin-producing cells

Nathan Sabin

Introduction: Type 1 diabetes, or T1D, is a disease resulting from autoantibody mediated destruction of insulin-producing pancreatic β cells1-3. Daily insulin injections have been the gold standard for treatment since 1922, however, inadequate levels of acute glucose control in diabetic patients leads to a higher risk of medical complications including ketoacidosis, kidney failure, cardiovascular diseases, neuropathy, and retinopathy4,5.  Transplantation of pancreatic islets containing functional β cells has proven to be an effective approach to achieving blood glucose homeostasis but the supply of transplantable cells is a limiting factor4. Procuring adequate sources of β cells is crucial to advancing this therapy. Several approaches seem promising, one being the in-vivo transdifferentiation of adult cells into insulin-producing cells4,5. Many of the transcription factors responsible for guiding pancreatic differentiation and proper development of β cells have previously been elucidated6. Overexpression of certain factors has been shown to cause in-vivo transdifferentiation of non-β cells to insulin-producing cells6-9. The development of a protocol to form new insulin-producing β cells is one that may lead to an effective, long-lasting treatment of T1D. Methods: Transgenic mouse models used Cre-recombinase to allow targeted expression of polypeptide tagged Mafa and Pdx1 in cells positive for either Ngn3 or Glucagon. Models either expressed Mafa, Pdx1, or Mafa+Pdx1. At the time of analysis, pancreatic tissues were fixed, antibody stained, and analyzed under fluorescence. The number of cells positive for insulin, glucagon, PP, and β-gal were manually counted. Results: Ngn3 positive β cell precursors which had overexpression of Mafa and Pdx1 in concert with one another showed a 9-fold increase in the number of insulin and glucagon copositive cells compared to cells only expressing Pdx1. These cells would resolve to become only insulin-positive within 6 weeks. Mafa also potentiated the effect of Pdx1 resulting in transdifferentiation effects in glucagon positive α cells whereas Pdx1 or Mafa alone were insufficient9. Conclusion: This work shows that Pdx1 and Mafa can work in concert to reverse terminal differentiation events in non-β cells which causes them to transdifferentiate into insulin-producing cells. With this, the potential is there to reverse the destruction of β cells and allow the regeneration of new β cells in patients with T1D.


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